Acumulating data suggest that thrapeutic drug therapeutic may optimize efficacity and tolerance of MMF. It could guarantee better exposure to the drug in the first 3 months and then minimize side effects in the long term. However definitive proof is still lacking. We conducted a randomized study in 11 french centers and included 137 kidney transplant recipients (PRA<50%) receiving a classical immunosuppressant regimen with basiliximab, Csa, MMF and steroids. The "fixed dose" group received 2 g of MMF a day. The "concentration controlled" group received MMF dose adapted to the area under the concentration curve (AUC) of MPA, with a target of 40 h.mg/L. After transplantation AUCs were calculated with a Bayesian estimator using a 3-point limited sampling strategy on day 7, 14, and months 1, 3, 6 , 12 in both groups (values note communicated to the physicians in the "fixed dose" group.